This invention relates to a vehicle tire deflator, i.e., a mechanism attachable to the filler valve of a vehicle tire to facilitate a tire-deflation operation. Such an operation is sometimes carried out by a military force when it is preparing to move one or more wheeled vehicles over soft terrain. A partially-deflated tire has an enlarged surface area in contact with the terrain so that unit pressure forces (p.s.i.) are relatively small; the tire is less apt to sink into the terrain and thus impede vehicle motion.
Various automatic tire inflation-deflation mechanisms and systems have been devised for adjusting or controlling air pressures within vehicle tires. However such automatic systems are relatively costly to implement into hardware, especially with vehicles having large numbers of tires, e.g., heavy equipment transporters used to transport military tanks or armored personnel carriers. One particular transporter has a total thirty wheel-tire assemblies, fourteen on the tractor and sixteen on the trailer. An automatic inflation-deflation system for such a vehicle would be relatively costly.
It is possible to carry out the tire-deflation operation manually, i.e., to manually depress and hold open the tire valve for a length of time, apply a pressure gage to the valve, and repeat the process until the desired tire pressure is obtained. However such a process is very time-consuming when the vehicle has a large number of tires, e.g. the previously mentioned heavy equipment transporter. Additionally, when the vehicle has some or all of the wheels arranged as dual wheels (two wheels alongside one another at each end of an axle) it is difficult to maintain access to valves on the inner tires in a given dual wheel set. The soldier is required to crawl or crouch in the area behind the outer wheel; reading a tire pressure gage while in a prone or crouched position is time-consuming, difficult and sometimes conducive to reading error.
The present invention is directed to a semi-automatic tire deflation device that can be attached to a tire valve (e.g. by screwing it onto the threaded stem area of the valve). The device is provided with a depressible plunger mechanism that can be operated to automatically open the tire valve and hold it open until the tire has been deflated to a predetermined pressure. For example, where the normal tire pressure is sixty p.s.i. the deflation device can be utilized to reduce the pressure to 30 p.s.i. As previously noted, the device is used primarily when it becomes necessary or desirable to appreciably reduce the tire pressure (i.e., increase the terrain contact area) preparatory to vehicle operation in soft soil.
One advantage of our delfation device is that once the plunger mechanism is operated the deflation operation proceeds automatically, i.e., the soldier can set the plunger and move on to the next tire without waiting for the first tire to deflate. When large numbers of tires are to be partially deflated there can be a considerable time savings.
Another advantage of our device is that the final pressure in each tire is substantially the desired pressure. Final pressure is achieved automatically without need for human readout of a pressure gage. Possibility for error in the final pressure is greatly minimized.